ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 155 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-simtec.c b/drivers/i2c/busses/i2c-simtec.c
new file mode 100644
index 000000000..b4ca256a0
--- /dev/null
+++ b/drivers/i2c/busses/i2c-simtec.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2005 Simtec Electronics
+ *	Ben Dooks <ben@simtec.co.uk>
+ *
+ * Simtec Generic I2C Controller
+*/
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+
+#include <linux/i2c.h>
+#include <linux/i2c-algo-bit.h>
+
+struct simtec_i2c_data {
+	struct resource		*ioarea;
+	void __iomem		*reg;
+	struct i2c_adapter	 adap;
+	struct i2c_algo_bit_data bit;
+};
+
+#define CMD_SET_SDA	(1<<2)
+#define CMD_SET_SCL	(1<<3)
+
+#define STATE_SDA	(1<<0)
+#define STATE_SCL	(1<<1)
+
+/* i2c bit-bus functions */
+
+static void simtec_i2c_setsda(void *pw, int state)
+{
+	struct simtec_i2c_data *pd = pw;
+	writeb(CMD_SET_SDA | (state ? STATE_SDA : 0), pd->reg);
+}
+
+static void simtec_i2c_setscl(void *pw, int state)
+{
+	struct simtec_i2c_data *pd = pw;
+	writeb(CMD_SET_SCL | (state ? STATE_SCL : 0), pd->reg);
+}
+
+static int simtec_i2c_getsda(void *pw)
+{
+	struct simtec_i2c_data *pd = pw;
+	return readb(pd->reg) & STATE_SDA ? 1 : 0;
+}
+
+static int simtec_i2c_getscl(void *pw)
+{
+	struct simtec_i2c_data *pd = pw;
+	return readb(pd->reg) & STATE_SCL ? 1 : 0;
+}
+
+/* device registration */
+
+static int simtec_i2c_probe(struct platform_device *dev)
+{
+	struct simtec_i2c_data *pd;
+	struct resource *res;
+	int size;
+	int ret;
+
+	pd = kzalloc_obj(struct simtec_i2c_data);
+	if (pd == NULL)
+		return -ENOMEM;
+
+	platform_set_drvdata(dev, pd);
+
+	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (res == NULL) {
+		dev_err(&dev->dev, "cannot find IO resource\n");
+		ret = -ENOENT;
+		goto err;
+	}
+
+	size = resource_size(res);
+
+	pd->ioarea = request_mem_region(res->start, size, dev->name);
+	if (pd->ioarea == NULL) {
+		dev_err(&dev->dev, "cannot request IO\n");
+		ret = -ENXIO;
+		goto err;
+	}
+
+	pd->reg = ioremap(res->start, size);
+	if (pd->reg == NULL) {
+		dev_err(&dev->dev, "cannot map IO\n");
+		ret = -ENXIO;
+		goto err_res;
+	}
+
+	/* setup the private data */
+
+	pd->adap.owner = THIS_MODULE;
+	pd->adap.algo_data = &pd->bit;
+	pd->adap.dev.parent = &dev->dev;
+
+	strscpy(pd->adap.name, "Simtec I2C", sizeof(pd->adap.name));
+
+	pd->bit.data = pd;
+	pd->bit.setsda = simtec_i2c_setsda;
+	pd->bit.setscl = simtec_i2c_setscl;
+	pd->bit.getsda = simtec_i2c_getsda;
+	pd->bit.getscl = simtec_i2c_getscl;
+	pd->bit.timeout = HZ;
+	pd->bit.udelay = 20;
+
+	ret = i2c_bit_add_bus(&pd->adap);
+	if (ret)
+		goto err_all;
+
+	return 0;
+
+ err_all:
+	iounmap(pd->reg);
+
+ err_res:
+	release_mem_region(pd->ioarea->start, size);
+
+ err:
+	kfree(pd);
+	return ret;
+}
+
+static void simtec_i2c_remove(struct platform_device *dev)
+{
+	struct simtec_i2c_data *pd = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&pd->adap);
+
+	iounmap(pd->reg);
+	release_mem_region(pd->ioarea->start, resource_size(pd->ioarea));
+	kfree(pd);
+}
+
+/* device driver */
+
+static struct platform_driver simtec_i2c_driver = {
+	.driver		= {
+		.name		= "simtec-i2c",
+	},
+	.probe		= simtec_i2c_probe,
+	.remove		= simtec_i2c_remove,
+};
+
+module_platform_driver(simtec_i2c_driver);
+
+MODULE_DESCRIPTION("Simtec Generic I2C Bus driver");
+MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:simtec-i2c");